PROJECTILE WEAPONS. 141 



will indeed cause it to withdraw its tentacles, and 

 contract its disk into that button-like shape which is 

 common to the genus ; but this is only for a moment : 

 it instantly expands again, and remains full blown 

 in spite of all its draggings about. Its skin also is 

 peculiarly tough and leathery; a provision, doubtless, 

 against the accidents to which its vagTant life 

 exposes it. 



We have no species which to such an extent as 

 this shoots forth those white filaments, which in this 

 family are weapons of oifence. On being alarmed or 

 rudely handled, from several of the warts on the body 

 the animal shoots forth these threads, which exactly 

 resemble white sewing-cotton, to the length of four or 

 even six inches ; and under circumstances of great 

 irritation an immense bundle of such threads is pro- 

 jected from the mouth. These filaments are not 

 wasted: they are shot out in a straight line, but remain 

 attached to the animal, and presently all trace of them 

 has disappeared. They are withdrawn again into 

 the hody.^ 



This curious result, which I did not anticipate, I 

 proved by carefully watching the process with a lens. 

 The naked eye can readily perceive that each thread 

 is gi'adually corrugated into small irregular coils at 

 that end which is next the animal, while the free end 

 remains straight. By applying a pocket-lens with a 

 power of 15 diameters to the affixed end, I perceived 



* I have since used the presence of this faculty for the purpose of 

 separating such Actiniae as possess it to form a genus, under the 

 name of Sagartia. — See a jMemoir on Peachia hastata, in the Linnean 

 Transactions for 1855, p. 267. {Second Edition.) 



